Nozzle for turbines.



W. PAPE. NOZZLE FOR TURBINES. mmommr FILED JULY 1v, 1912.

Patented Jan. 27, 1914.

Emir, HELJW PARE,

STATES ATENT FFE.'

WILHELM PAPE, 0F CHARLOTTENBURG, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY. A CORPORATION OF NEW YORK.

NOZZLE FOR TURBINES.

:lessees To all whom 'it may marc/'n Be it known that l. lFinHnL-M Parr., a subject of the Emperor ot Germany, residing at Charlottenburg, Germany. have invented certain .new and useful Improvements in `Nozzles Yfor Turbines, ot which the Yfollowing is a specification.

This invention relates to nozzles for elastic tiui'd turbines and its object is to provide a nozzle in which the elastic fluid can ex` pand to the final pressure easily, whether or not this pressure is above or below that for which the nozzle is designed, and. without. changing appreciably the angle of the jet.

Tests have shown that a jet of steam in passing out et a tubular nozzle which has been cut oli1 on a plane oblique to its axis is defiected very considerably from its original direction whenever the ratio of the pressures preceding and following its course through said nozzle is greater than the crit-ical ratio; that is, a ratio of 1.7 for dry saturated steam. inasmuch as the nozzle is so placed as to direct the jet in line with the surface ot` the bucket at the edge thereof, itfollows that any such deflection impairs the ehciency of the engine, because there is a considerable impact upon the back ofthe bucket. This deflection ot the steam jet is caused by the fact that the boundary walls of the nozzle permit the jet to broadenonly in a direction at an angle to its axis, and the deflection from the axis of the nozzle becomes greater in accordance with the increase over the critical steam velocity as the jet leaves the nozzle. rlhis tendency to expand in a direction oblique to the of the nozzle is more marked with a4 nozzle whose cross .section is uniform throughout; but it occurs to a greater or less degree in the nozzles of the expanding type, when the iinal pressure is above or below the correct value. My invention aims to correct this tendency of the jet to diverge in this inetlicieiit manner, and to this end it. comprises anozzle so constructed that the enlargement of the steam jet is only partially limited by the walls ot said nozzle, and the expansion ot' said jet can therefore take place unhindcrcd in accordance with the pressures preceding and following the nozzle. This result may be obtained in a simple manner by causing the smallest cross scctiowof the nozzle to Specication of Letters Patent.

Application filed July 17. 1912.

Patented Jan. 27,1914. seriai No. 709,872.

coincide practically with the cross section of the opening into the receiving chamber.

The invention will be better understood by reference to the accompanying drawing, in

Figure 1 is an axial section of a nozzle as ordinarily constructed; Fig. 2 is a transverse section of the same; Fig. 3 is an axial section ot' my improved nozzle; Fig. 4 is a transverse section thereof; Fig. 5 is a similar sccticn of a modification; and FigsfG, 7 and 8 show the action of the improved nozzle with varying pressures.

The old -torm of nozzle 1 shown in Figs. l and 2 has its mouth cut ott on a line cz which is oblique to its axis b. The lilies c indicate how the steam jet will be deflected from the axial direction whenever the Velocity varies from the critical. In this form ot nozzle, the top and bottom walls Q, 3 are parallel. If these walls should diverge to form the usual expanding nozzle, the jet of steam will remain in its original direction at velocities above the critical velocity,V

but the nozzle will give a maximum etliciency only for the pressure ratio upon which the calculation is based, while at every other ratio of expansion the efficiency falls ott considerably.

1f the nozzle is constructed with a greater expansion than that. which corresponds lto the ratio of pressures preceding and following the nozzle, then the steam pressure follows the free expansion too far below the ti'ue coiiiitei'-1 i'essuie, rising thereafter by impulses to the said counter-pressure. The pulsations ot' compression in the broadeiied part of the nozzle result in an impairment. of ethciency. My invention avoids the disadvantages of these two forms of nozzle by adopting the construction shown in Figs. 3 to 8. The side walls 4; of the nozzle may be either parallel, as shown in Fig. 4, or they may diverge at the lower edges, as shown in Fig. 5; the latter construction permittingl a beneficial expansion of the jet in these directions as well. The bottom 5 oi' the nozzle is parallel with thc terminal portion G ot the top, but. that portion 7 of the top between such termina-l portion and the throat. S of the nozzle is oblique to the 105 axis oi said nozzle` so as to contract it in cross section toward the throat, which is located so as to coincide with the rear end or edge of said mouth. In such a nozzle, with velocity,

only a `partial limitation of the steam jet passage', the steam flows in a close jet in the direction of the axis of the nozzle out into the receiving chamber. The reason of this is that the instant the steam passesthe narrow throat it can expand not only upwardly toward the top of the nozzle, but also unrestrictedly on thev under side toward the receiving chamber. At a velocity of 800 to 1000 meters per second, the jet will assume the form shown in Fig. 6. At a lower velocity, say about 500 to 700 meters per second, the jet will expand'only upwardly, the under side of the jet remaining practically in line parallel with the axis of the nozzle, as shown in Fig. 7. "With still smaller steam from the critical value downward, the jet of steam'issues at a flatter angle than that of the nozzle axis, as shown in Fig. S, which is' an advantage because yof the greater ease with which it enters the bucket. YSince the enlarged portion of the steam jet is not bounded on all sides, the steam expands down. only to the true counter-pressure, so that any compressionpulsations are avoided. l

The principal advantages of the invention are the following :-(l) No substantial deiection of the jet from the axis of the nozzle at high velocity. (2) No under-expansion, and therefore no compression-pulsations at a smaller ratio of -expansion than that which corresponds to the ressure ratio upon which the calculation is asedi (3) At steam velocities below the critical'velocity, the exit' of the steam is effected at a flatter angle than that given by the axis of the nozzle, so that the axial cross section of exit is entirely filled, and when nozzles are ranged side by side a close band` ofsteanl is obtained; (4:)- The part of the nozzle, through which the steam flows at high velocity is of minimum length, and accordingly the friction losses also are reduced to a minimum, resulting 1n better eiiicleney.

lits bottom at the In accordance with .the provisions of the patent statutes, I have described the principle of operation of myinvention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can other means.

lNhat I claim as new and desire to secure by Letters Patent of the United States, is,-

l. An expanding nozzle for elastic fluid turbines having its throat coincident with the rear end of its mouth and its top at and beyond the throatfextending obliquely upward with reference tothe directionof throat, so that the jet of fluid discharged from it may expand freely after passi'ngthe throat without being deflected downward.

2. An expanding nozzle for elastic fluid turbines having a. 'diverging yond its throat, and the bot-tom of its expanding portion cut away to the point'of smallest cross section of said nozzle, so that the jet of fluid discharged from it may ex pand freely after passing the throat without being deflected downward.

3. An expanding nozzle in which the exbe carried out by' I top at and bepansion of the steam iet beyond the throat of the nozzle 1s unrestricted on its `under side, and 1n which the terminal portion of the top is substantially parallel with the bot- WILHELM Para.

-Vit-nesses: HENRY I-IAsrEn, IVOLDEMAR HAUPT., 

